WO2006114972A1 - Semiconductor photoelectrode, method for manufacturing such semiconductor photoelectrode and light energy converting device - Google Patents

Semiconductor photoelectrode, method for manufacturing such semiconductor photoelectrode and light energy converting device Download PDF

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Publication number
WO2006114972A1
WO2006114972A1 PCT/JP2006/306465 JP2006306465W WO2006114972A1 WO 2006114972 A1 WO2006114972 A1 WO 2006114972A1 JP 2006306465 W JP2006306465 W JP 2006306465W WO 2006114972 A1 WO2006114972 A1 WO 2006114972A1
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WO
WIPO (PCT)
Prior art keywords
semiconductor
semiconductor photoelectrode
metal substrate
photoelectrode according
metal
Prior art date
Application number
PCT/JP2006/306465
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French (fr)
Japanese (ja)
Inventor
Takashi Oi
Yasukazu Iwasaki
Kazuhiro Sayama
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Nissan Motor Co., Ltd.
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Publication date
Application filed by Nissan Motor Co., Ltd. filed Critical Nissan Motor Co., Ltd.
Priority to EP06730413A priority Critical patent/EP1873277A4/en
Priority to US11/911,977 priority patent/US7961452B2/en
Publication of WO2006114972A1 publication Critical patent/WO2006114972A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/20—Light-sensitive devices
    • H01G9/2027—Light-sensitive devices comprising an oxide semiconductor electrode
    • H01G9/2031—Light-sensitive devices comprising an oxide semiconductor electrode comprising titanium oxide, e.g. TiO2
    • B01J35/39—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/50—Processes
    • C25B1/55—Photoelectrolysis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/20—Light-sensitive devices
    • H01G9/2027—Light-sensitive devices comprising an oxide semiconductor electrode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/20—Light-sensitive devices
    • H01G9/209—Light trapping arrangements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/20—Light-sensitive devices
    • H01G9/2095—Light-sensitive devices comprising a flexible sustrate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/063—Titanium; Oxides or hydroxides thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/24—Chromium, molybdenum or tungsten
    • B01J23/30—Tungsten
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/542—Dye sensitized solar cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a semiconductor photoelectrode applied to a hydrogen production apparatus that generates hydrogen by decomposing water with light energy, a method for producing the same, and a light energy conversion device using the semiconductor photoelectrode.
  • TiO single crystal or TiO powder is sintered and pelletized.
  • TiO sintered pellets are used. However, if TiO single crystals are used, manufacturing costs
  • FIG. 11 shows a semiconductor photoelectrode 40 using a titanium plate as a metal substrate.
  • a Ti plate is baked to form a TiO layer on the Ti plate.
  • a semiconductor layer (TiO layer) 42 is formed thereon. In this way, the Ti plate is baked and the
  • Producing the conductor layer 42 can reduce manufacturing costs and further improve the flexibility of semiconductor photoelectrodes.
  • the charge transfer distance in the semiconductor layer 42 becomes longer, and the rate of recombination of the generated electrons and holes may increase.
  • the charge movement speed in the semiconductor layer 42 is slow, if the charge movement distance is long, the photoelectric conversion efficiency is reduced.
  • the surface of the conventional semiconductor photoelectrode 40 is flat, if the incident light is reflected, the light absorption efficiency is reduced.
  • the present invention has been made to solve the above-described problems, and an object of the present invention is to improve a light absorption efficiency and prevent charge recombination, a method for manufacturing the semiconductor photoelectrode, and a photoelectric device. An object of the present invention is to provide a light energy conversion device with improved conversion efficiency.
  • the semiconductor photoelectrode according to the first aspect of the present invention has a metal substrate having irregularities on the surface, and a semiconductor layer made of a material having a photocatalytic action, which is formed on the surface of the metal substrate. It is characterized by that.
  • the method for producing a semiconductor photoelectrode according to the second aspect of the present invention includes a step of forming a metal substrate having irregularities on the surface, and a semiconductor layer made of a material having a photocatalytic action on the surface of the metal substrate. And a step of creating.
  • FIG. 1 is an enlarged cross-sectional view showing a semiconductor photoelectrode according to an embodiment of the present invention.
  • FIG. 2 is a diagram for explaining an interval of unevenness.
  • FIG. 3 is a plan view showing a metal substrate used for a semiconductor photoelectrode.
  • FIG. 4 shows a configuration of a hydrogen production apparatus using a semiconductor photoelectrode according to an embodiment of the present invention. It is the schematic which shows composition.
  • FIG. 5 is a diagram for explaining the principle of operation for decomposing water by the hydrogen production apparatus shown in FIG. 4.
  • FIG. 6 is a diagram showing a configuration of a three-electrode experimental apparatus used in Examples and Comparative Examples.
  • FIG. 7 is a view showing a steel plate used in Example 4 and Example 5, (a) is a top view of a Ti plate, and (b) is a Ti plate shown in (a). It is AA 'sectional drawing of a board.
  • FIG. 8 is a graph showing the measurement results of the photocurrent values for Examples 1 to 3 and Comparative Examples 1 to 3.
  • FIG. 9 is a graph showing the measurement results of photocurrent values for Example 4, Example 5, and Comparative Example 3.
  • FIG. 10 is a graph showing the measurement results of photocurrent values for Example 6 and Comparative Example 4.
  • FIG. 11 is an enlarged cross-sectional view showing a conventional semiconductor photoelectrode.
  • a semiconductor photoelectrode according to an embodiment of the present invention, a manufacturing method thereof, and a semiconductor photoelectrode are used.
  • the V light energy converter will be explained.
  • FIG. 1 shows the surface state of the semiconductor photoelectrode 1 according to the embodiment of the present invention.
  • the semiconductor photoelectrode 1 includes a metal substrate 2 having a high surface area by forming irregularities on the surface, and a semiconductor layer 3 formed on the surface of the metal substrate 2.
  • the unevenness on the surface of the metal substrate 2 is formed on the average as much as possible and the groove is deep.
  • the arithmetic average roughness (Ra) of the surface of the metal substrate 2 is preferably in the range of 1 ⁇ to 4 / ⁇ m. The reason for this is that a higher photocurrent value can be obtained within this range.
  • the arithmetic average roughness (Ra) of the surface of the metal substrate 2 is a value obtained from the following equation using a roughness meter (Tencor Alpha Step). In Equation 1, 1 is a reference length, and x) is a curve along the roughness of the shape of the metal substrate 2 surface.
  • the maximum height (Ry) is preferably in the range of 1 to 500 ⁇ m, and more preferably in the range of 3 to 200 ⁇ m.
  • the maximum height (Ry) is the total value (x + y) of the distance between the average line of the concavo-convex shape and the maximum convex portion (X) and the distance between the average surface of the concavo-convex shape and the minimum concave portion (y).
  • the arithmetic average roughness (Ra) and the maximum height (Ry) can be determined according to JIS BO 601 (ISO 4287).
  • the unevenness interval is 500 ⁇ m or less and is as dense as possible.
  • the interval between the projections and depressions indicates the interval 34 between adjacent projections in the surface roughness curve 33 as shown in FIG. Reference numeral 32 in FIG. 2 represents an average line.
  • the metal substrate 2 a single element or a composite of the element (oxide, nitride, white nitride, oxynitride, sulfide, oxysulfide, etc.) can be used. These materials can exhibit photocatalytic properties or photoelectrode properties. Specifically, it is preferable to use, as the metal substrate, at least one element selected from among Ti, Nb, Ta, W, V, Co, Fe, Ni and In and a composite thereof.
  • a material having a photocatalytic action can be used. Specifically, TiO, Nb 0, Ta 0, WO, V 0, InCuTaO, InNiTaO, InCoTaO, InFeTaO, InMn
  • the material of the semiconductor layer 3 may be different from the metal compound forming the metal substrate 2.
  • the thickness of the semiconductor layer 3 is preferably in the range of 0.1 m to l ⁇ m. If the thickness of the semiconductor layer 3 is less than 0 .: L m and becomes too thin, the light absorption efficiency decreases. On the other hand, if the thickness force m is exceeded, the charge transfer distance becomes long, so that the charge transfer becomes slow or the charges are recombined.
  • the metal substrate 2 having irregularities on the surface is prepared.
  • a method for forming the unevenness a method of performing chemical etching after mechanically polishing the metal plate can be used.
  • the maximum height (Ry) is preferably 1 ⁇ m to 500 ⁇ m, and more preferably 3 ⁇ m to 200 ⁇ m.
  • the unevenness interval is set to 500 m or less to narrow the unevenness interval. It is preferable.
  • the metal plate may be prepared by rough polishing using a polishing paper or the like.
  • a porous body having irregularities on the surface formed by joining metal particles 36 by pressure or heat can also be used.
  • the particle size (D50) of the metal particles 36 used at this time is preferably in the range of 1 m to 400 ⁇ m, preferably 3 ⁇ m to 200 ⁇ m.
  • the metal substrate 35 in FIG. 3 has the metal particles 36 arranged in an orderly manner both vertically and horizontally.
  • the metal substrate of the present invention is not limited to this, and any porous material formed by joining metal particles by pressure or heat.
  • the body can be used.
  • the size distribution for measuring the size distribution (range and content).
  • the particle size distribution is generally expressed as a (percentage) weight percentage by using several sieves with different openings and measuring the percentage passing through the openings. Since the metal particles used in the present invention are several / zm level, they are measured using a general particle size distribution meter, and the particle size having an integrated value of 50% is defined as “particle size (D50)”.
  • the semiconductor layer 3 is formed on the obtained metal substrate 2, and the manufacturing method of the semiconductor layer 3 differs depending on the raw material used.
  • the semiconductor layer 3 also has simple acidity and physical strength
  • a metal substrate made of a simple metal is baked or electrolytically oxidized in an oxidizing atmosphere (in air or oxygen).
  • the metal substrate made of the simple metal is heated or plasma-treated in a non-oxidizing atmosphere (ammonia, nitrogen, hydrogen sulfide, etc.).
  • a non-oxidizing atmosphere ammonia, nitrogen, hydrogen sulfide, etc.
  • oxynitrides containing transition metal ions with a d-type electron configuration such as Ta 5+ and Ti 4+ (eg TaON), nitrogen-doped semiconductors (eg ⁇ : N), oxysulfide, etc.
  • the semiconductor layer 3 which also has a force, from a simple metal
  • the semiconductor layer 3 is composed of a composite metal semiconductor
  • a composite metal precursor is applied onto the metal substrate 2, and then any one of oxidation, nitridation, and sulfur treatment is performed to form the semiconductor layer 3. create.
  • post treatment may be performed by oxidation, hydrogen reduction, or steam.
  • Post-processing can reduce or increase lattice defects in the semiconductor layer 3. Note that increasing the number of lattice defects in the semiconductor layer 3 increases the conductivity.
  • FIG. 4 shows the configuration of a hydrogen production apparatus 6 using the semiconductor photoelectrode of the present invention.
  • a semiconductor photoelectrode 8 working electrode
  • a counter electrode 9 for example, a Pt electrode and a carbon electrode
  • An ion exchange membrane 12 is attached to the middle position of 7.
  • an external short-circuit wire 10 is created by connecting a conductor to the semiconductor photoelectrode 8 and the counter electrode 9.
  • an electrolyte solution 11 for example, Na SO aqueous solution
  • a stable supporting electrolyte is stored in order to reduce the solution resistance of the electrolytic reaction.
  • the semiconductor photoelectrode 8 is irradiated with sunlight 13 to electrolyze water.
  • the material of the counter electrode 9 can be selected according to the reaction. In order to generate hydrogen, Pt electrode and carbon electrode with low hydrogen overvoltage are effective. Any Co-Mo electrode may be used. As the supporting electrolyte, NaOH, Na 2 SO 4, H 2 SO 4 and Na 2 HPO which are used as electrolytes for general electrolytic reactions can be used. Supporting electrolysis
  • the concentration of the material should be higher than 0. Olmol / L in order to reduce the overvoltage of electrolysis.
  • a reducing reactant that can be easily decomposed by the photocatalyst for example, an organic substance, hydrogen sulfide, or iodine ion
  • the electrolyte solution 11 may contain a reducing reactant that can be easily decomposed by the photocatalyst (for example, an organic substance, hydrogen sulfide, or iodine ion) in the electrolyte solution 11. This can increase the photoelectric conversion efficiency.
  • the reaction area between the photocatalyst (semiconductor layer) and the reaction substrate is widened, so that it is less susceptible to light scattering. For this reason, the photoelectric conversion efficiency is remarkably increased as compared with the conventional electrode.
  • a bias potential or a source meter may be installed on the external short-circuit line 10 to control the bias potential.
  • an artificial light source for example, a xenon lamp
  • a xenon lamp may be applied instead of the sunlight 13.
  • the generated electrons 16 move to the metal substrate 2 in the semiconductor photoelectrode 8, and then move to the counter electrode 9 through the external short line 10.
  • This electron (e_) reduces water on the counter electrode 9 and generates hydrogen 17 by the reaction shown in Equation 2.
  • the semiconductor photoelectrode is not limited to the water electrolysis apparatus, and is dye-sensitized. It can also be applied as a light energy conversion device such as a type solar cell.
  • a three-electrode experimental apparatus 18 shown in FIG. 6 has a semiconductor photoelectrode 20 as a working electrode and a Pt electrode 21 as a counter electrode disposed in a water tank 19, and the semiconductor photoelectrode 20 and the Pt electrode 21 are externally connected.
  • the short-circuit wire 22 is connected and made conductive.
  • a reference electrode serving as a reference electrode for setting and controlling the potential of the working electrode is disposed in another water tank 23, and a silver-silver chloride electrode (Ag-AgCl electrode) 24 is provided as the reference electrode.
  • Ag-AgCl electrode silver-silver chloride electrode
  • the two water tanks 19 and 23 are connected by a Vycor glass frit 25 to maintain electrical continuity between the semiconductor photoelectrode 20 and the Pt electrode 21.
  • An ammeter 26 is installed on the external short-circuit line 22 connecting the semiconductor photoelectrode 20 and the Pt electrode 21 to measure the photocurrent value flowing through the circuit.
  • a potentiostat 27 is installed on the external short-circuit wire 22, and the potentiostat 27 and the Ag-AgCl electrode 24 are connected by the external short-circuit wire 28.
  • the potentiostat 27 controls the potential difference between the semiconductor photoelectrode 20 and the Ag-AgCl electrode 24 by passing a current according to the potential.
  • an Na SO aqueous solution having a concentration of 0.1 mol / L is stored. This Na SO water
  • the 2 4 2 4 solution plays a role in charge transfer in the circuit when a potential difference occurs between the semiconductor photoelectrode 20 and the Pt electrode 21.
  • a xenon lamp (500 W) 29 is disposed outside the water tank 19 in which the semiconductor photoelectrode 20 is disposed, and a chopper 30 is disposed between the xenon lamp 29 and the semiconductor photoelectrode 20.
  • the light applied to the semiconductor photoelectrode 20 by the chopper 30 is switched at regular intervals.
  • a Ti porous body prepared by necking Ti metal particles having an average particle diameter of 45 m by heating and pressing was used as the metal substrate 2.
  • the arithmetic average roughness (Ra) of the porous Ti material was about 2 ⁇ m, and the maximum height (Ry) was about 5 ⁇ m.
  • This Ti porous body was heat-treated for 1 hour in an air atmosphere while changing the temperature in the range of 500 ° C to 700 ° C.
  • the heat treatment temperature was 500 ° C in Example 1, 600 ° C in Example 2, and 700 ° C in Example 3.
  • the surface of the porous Ti body is oxidized by heat treatment to create a TiO layer.
  • the thickness of the TiO layer varies depending on the measurement location.
  • Example 1 was 100 nm
  • Example 2 was 200 nm
  • Example 3 was 600 m.
  • a Ti flat plate was used in place of the Ti porous body used in Examples 1 to 3.
  • the arithmetic average roughness (Ra) of the Ti flat plate was 0.2 ⁇ m to 0.3 ⁇ m. Moreover, no large irregularities were created on the surface of the Ti plate, and the maximum height (Ry) was less than 1 ⁇ m.
  • a semiconductor photoelectrode was manufactured using a method similar to the manufacturing method shown in Examples 1 to 3 except that a Ti flat plate was used. The thickness of the TiO layer varies depending on the measurement location
  • Comparative Example 1 was 100 nm
  • Comparative Example 2 was 200 nm
  • Comparative Example 3 was 600 m.
  • Example 4 and Example 5 as the metal substrate 2, a Ti plate 31 in which a Ti flat plate was patterned with a photoresist mask and etched to create irregularities on the surface was used.
  • the surface of the Ti plate had the shape shown in Fig. 7 (a).
  • Fig. 7 (b) shows the AA 'cross section of the Ti plate surface shown in Fig. 7 (a).
  • X and Y shown in FIG. 7 (b) were 5 m and 70 m, respectively, and in Example 5, X and Y were 40 m and 70 m, respectively.
  • Ra arithmetic mean roughness
  • the obtained Ti plate was heat-treated at 700 ° C for 1 hour in an air atmosphere to oxidize the Ti plate surface to form a TiO layer.
  • the thickness of the TiO layer varies depending on the measurement location,
  • the implementation f row was 4 ⁇ m up to 600 ⁇ m, and the implementation f row 5 up to 600 ⁇ m.
  • Example 6 first, a hydrated colloid of WO was prepared.
  • WO hydrate colloids are ions
  • This hydrated colloidal aqueous solution was mixed with an equal volume of ethanol and then distilled under reduced pressure (60 ° C) to reduce its volume to 1/4. Thereafter, 1/2 amount of polyethylene glycol 300 (manufactured by Wako Pure Chemical Industries, Ltd.) was added and mixed using a stirrer to obtain a colloidal slurry of WO.
  • the assemblage was uneven, but the layer thickness was not uniform, so the layer thickness was not measurable.
  • Comparative Example 4 using the slurry produced in Example 6, this slurry was applied on the Ti flat plate used in Comparative Example 1, and then heat-treated at 500 ° C. for 1 hour to form a WO layer on the Ti flat plate.
  • the WO layer is an aggregate of particles with irregularities but not a uniform thickness.
  • Example 1 2 .0 5 .0 0 .1 1 2 0
  • Example 2 2 .5 5 .0 .2 3 2 0
  • Example 3 2 .0 5 .0 .6 4 0 0
  • Example 4 3. 0 1 0 5 .6 3 0 0
  • Example 5 3 .3 8 .8 0 .6 3 2 0
  • Comparative Example 1 ⁇ 0.2 ⁇ ⁇ 0.3 1 Less than 0.1 8 0 Comparative Example 2 0.2-0. 3 Less than 1 0.2 9 5 Comparative Example 3 0.2 ⁇ 0. 3 Less than 1 0.6 1 4 0
  • Example 6 2 0 5 .- 5 5 0
  • Comparative Example 4 0.2 ' ⁇ 0. 3 1 Less than-3 1 0
  • Example 1 to Example 3 using a porous Ti material unevenness was created on the surface of the semiconductor photoelectrode. It is because it can also absorb. Further, it is possible to prevent charge recombination by increasing the substantial surface area of the semiconductor layer and lowering the charge density in the semiconductor layer. Furthermore, when electrons move through the metal substrate rather than the semiconductor layer, the resistance is small and advantageous. Therefore, increasing the area of the metal substrate is a force that can shorten the distance of charge transfer from the semiconductor layer to the metal substrate. .
  • Example 4 Example 5, and Comparative Example 3
  • the results of measuring the photocurrent value are shown in FIG.
  • Fig. 9 the photocurrent values of Example 4 and Example 5 using a plate with irregularities on the surface increased by about 2 times compared to Comparative Example 3 using a Ti flat plate. It was proved that, as in Examples 1 to 3 described above, it is effective to provide unevenness on the metal substrate.
  • Example 6 In Example 6 and Comparative Example 4, only the light absorption characteristics of WO are considered separately.
  • Example 1 a sintered Ti porous body was used as a substrate. You may use the semiconductor photoelectrode which formed the unevenness
  • a method of supporting the photocatalyst on the metal substrate a method of applying a heat treatment after applying the paste-like photocatalyst on the metal substrate has been shown.
  • the present invention is not limited to this method.
  • the photocatalyst may be supported on the metal substrate by physical vapor deposition or chemical vapor deposition.
  • the substance that can be oxidized by using water as an example of a substance that is oxidized by holes is not limited to water.
  • an organic substance such as factory waste water is used to convert the organic substance into an organic substance. Oxidation as a sacrificial reagent is also conceivable.
  • the chemical etching method was mentioned as a method for creating irregularities on the surface, but the present invention is not limited to this, and irregularities are created on the surface by ion etching, LIGA process or anodizing. You can do it.
  • the semiconductor photoelectrode of the present invention it is possible to increase the light absorption efficiency and prevent charge recombination.
  • the method for producing a semiconductor photoelectrode of the present invention it is possible to easily produce a semiconductor photoelectrode having an uneven surface formed to increase the surface area.
  • the photoelectric conversion efficiency can be increased because the semiconductor photoelectrode that has high light absorption efficiency and can prevent charge recombination can be used.

Abstract

A semiconductor photoelectrode is provided with a metal substrate having an uneven surface, and a semiconductor layer which is formed on a surface of the metal substrate and composed of a material having photocatalytic characteristics. Thus, light absorption efficiency is improved, and furthermore, charge recombination can be prevented.

Description

半導体光電極、その製造方法及び光エネルギ変換装置  Semiconductor photoelectrode, manufacturing method thereof, and light energy conversion device
技術分野  Technical field
[0001] 本発明は、光エネルギによって水を分解して水素を生成する水素製造装置に適用 される半導体光電極、その製造方法及び半導体光電極を用いた光エネルギ変換装 置に関する。  TECHNICAL FIELD [0001] The present invention relates to a semiconductor photoelectrode applied to a hydrogen production apparatus that generates hydrogen by decomposing water with light energy, a method for producing the same, and a light energy conversion device using the semiconductor photoelectrode.
背景技術  Background art
[0002] 太陽エネルギを有効利用するために、太陽エネルギを利用し易い形態に変換、貯 蔵する技術の開発が盛んに行われている。太陽電池はその代表例である力 コスト が高いことから普及が進んでおらず、より安価なシステムの開発が望まれている。  [0002] In order to effectively use solar energy, technology for converting and storing solar energy into a form that can be easily used has been actively developed. Solar cells are not popular because of their high power cost, which is a typical example, and the development of cheaper systems is desired.
[0003] そこで、光触媒を利用して光エネルギをィ匕学エネルギに変換する技術の研究が進 められている。光触媒に太陽光を照射すると、光触媒は、光エネルギを吸収して電子 と正孔を生成し、化学反応を引き起こす。光触媒の中でも、特に、二酸化チタン (ΉΟ  [0003] Therefore, research on technology for converting light energy into energy using a photocatalyst is underway. When the photocatalyst is irradiated with sunlight, the photocatalyst absorbs light energy and generates electrons and holes, causing a chemical reaction. Among photocatalysts, titanium dioxide (ΉΟ
2 )は価電子帯の位置が深いことから、生成した正孔による酸ィ匕カは、塩素あるいはォ ゾンよりも強いとされている。そのため TiOを半導体光電極として用いて、水を分解す In 2), since the position of the valence band is deep, it is said that the oxidant due to the generated holes is stronger than chlorine or ozone. Therefore, TiO is used as a semiconductor photoelectrode to decompose water.
2  2
る方法が研究されている（A.Fujishima and K.Honda, Nature, 238(5358), 37(1972)参 照)。  (See A. Fujishima and K. Honda, Nature, 238 (5358), 37 (1972)).
[0004] これまで半導体光電極としては、 TiO単結晶あるいは TiO粉末を焼結してペレット  [0004] Conventionally, as a semiconductor photoelectrode, TiO single crystal or TiO powder is sintered and pelletized.
2 2  twenty two
化した TiO焼結ペレットが使用されている。しかし TiO単結晶を使用すると、製造コス  TiO sintered pellets are used. However, if TiO single crystals are used, manufacturing costs
2 2  twenty two
トが高くなり、また、 TiO焼結ペレットを使用すると、光電変換効率が低くなつていた。  When TiO sintered pellets were used, the photoelectric conversion efficiency was low.
2  2
[0005] そこで、近年、導電性ガラスあるいは平滑な金属から形成される基板上に半導体層 を作成した半導体光電極が開示されている（J.Phys.Chem., 102(1998)7820及び J.Phy s.Chem.,98(1994)5552参照）。しかし、基板として導電性ガラスを使用すると、コストが 高くなり、さらに基板と半導体層との界面の密着性や安定性が低下してしまうことがあ る。したがって、基板として金属基板を用いた半導体光電極の開発が進められている  [0005] Therefore, in recent years, semiconductor photoelectrodes in which a semiconductor layer is formed on a substrate formed of conductive glass or a smooth metal have been disclosed (J. Phys. Chem., 102 (1998) 7820 and J. Phy s. Chem., 98 (1994) 5552). However, when conductive glass is used as the substrate, the cost is increased, and the adhesion and stability of the interface between the substrate and the semiconductor layer may be lowered. Therefore, development of a semiconductor photoelectrode using a metal substrate as a substrate is underway.
[0006] 図 11では、金属基板としてチタン板 (Ή板)を用いた半導体光電極 40を示している 。半導体光電極 40は、 Ti板を焼成して Ti板上に TiO層を作成し、これにより基板 41 [0006] FIG. 11 shows a semiconductor photoelectrode 40 using a titanium plate as a metal substrate. . For the semiconductor photoelectrode 40, a Ti plate is baked to form a TiO layer on the Ti plate.
2  2
上に半導体層 (TiO層） 42を作成している。このように Ti板を焼成してその表面に半  A semiconductor layer (TiO layer) 42 is formed thereon. In this way, the Ti plate is baked and the
2  2
導体層 42 (TiO層）を作成すると、製造コストを削減でき、さらに半導体光電極をフレ  Producing the conductor layer 42 (TiO layer) can reduce manufacturing costs and further improve the flexibility of semiconductor photoelectrodes.
2  2
キシブルにできると 、う利点を有して 、た。  Having a kisible has the advantage of being able to make it.
発明の開示  Disclosure of the invention
[0007] し力しながら、従来の金属基板を用いた半導体光電極の光電変換効率は、それほ ど高くない。そのため半導体層 (TiO層） 42を厚くすることで光の吸収効率を高め、  [0007] However, the photoelectric conversion efficiency of a semiconductor photoelectrode using a conventional metal substrate is not so high. Therefore, increasing the semiconductor layer (TiO layer) 42 increases the light absorption efficiency,
2  2
光電変換効率を向上させた半導体光電極も開発されている。  Semiconductor photoelectrodes with improved photoelectric conversion efficiency have also been developed.
[0008] ところが、半導体層 42を厚くすると、半導体層 42中での電荷の移動距離が長くなり 、生成した電子と正孔とが再結合する割合が高くなる可能性があった。また、半導体 層 42中での電荷の移動速度は遅いため、電荷の移動距離が長くなると、光電変換 効率が低下する要因となっていた。さらに、図 11に示すように、従来の半導体光電極 40は、その表面が平坦であることから、入射光が反射すると光の吸収効率が低下す る要因となっていた。 However, when the semiconductor layer 42 is thickened, the charge transfer distance in the semiconductor layer 42 becomes longer, and the rate of recombination of the generated electrons and holes may increase. In addition, since the charge movement speed in the semiconductor layer 42 is slow, if the charge movement distance is long, the photoelectric conversion efficiency is reduced. Furthermore, as shown in FIG. 11, since the surface of the conventional semiconductor photoelectrode 40 is flat, if the incident light is reflected, the light absorption efficiency is reduced.
[0009] 本発明は、上記課題を解決するためになされたものであり、その目的は、光の吸収 効率を高め、さらに電荷の再結合を防止した半導体光電極及びその製造方法、さら に光電変換効率を高めた光エネルギ変換装置を提供することにある。  [0009] The present invention has been made to solve the above-described problems, and an object of the present invention is to improve a light absorption efficiency and prevent charge recombination, a method for manufacturing the semiconductor photoelectrode, and a photoelectric device. An object of the present invention is to provide a light energy conversion device with improved conversion efficiency.
[0010] 本発明の第一の態様に係る半導体光電極は、表面に凹凸を有する金属基板と、前 記金属基板の表面に作成され、光触媒作用を有する材料から成る半導体層と、を有 することを特徴とする。  [0010] The semiconductor photoelectrode according to the first aspect of the present invention has a metal substrate having irregularities on the surface, and a semiconductor layer made of a material having a photocatalytic action, which is formed on the surface of the metal substrate. It is characterized by that.
[0011] 本発明の第二の態様に係る半導体光電極の製造方法は、表面に凹凸を有する金 属基板を作成する工程と、前記金属基板の表面に光触媒作用を有する材料から成 る半導体層を作成する工程と、を有することを特徴とする。  [0011] The method for producing a semiconductor photoelectrode according to the second aspect of the present invention includes a step of forming a metal substrate having irregularities on the surface, and a semiconductor layer made of a material having a photocatalytic action on the surface of the metal substrate. And a step of creating.
図面の簡単な説明  Brief Description of Drawings
[0012] [図 1]図 1は、本発明の実施の形態に係る半導体光電極を示す拡大断面図である。  FIG. 1 is an enlarged cross-sectional view showing a semiconductor photoelectrode according to an embodiment of the present invention.
[図 2]図 2は、凹凸の間隔を説明するための図である。  [FIG. 2] FIG. 2 is a diagram for explaining an interval of unevenness.
[図 3]図 3は、半導体光電極に用いられる金属基板を示す平面図である。  FIG. 3 is a plan view showing a metal substrate used for a semiconductor photoelectrode.
[図 4]図 4は、本発明の実施の形態に係る半導体光電極を用いた水素製造装置の構 成を示す概略図である。 [FIG. 4] FIG. 4 shows a configuration of a hydrogen production apparatus using a semiconductor photoelectrode according to an embodiment of the present invention. It is the schematic which shows composition.
[図 5]図 5は、図 4に示す水素製造装置により水を分解する動作原理を説明する図で ある。  FIG. 5 is a diagram for explaining the principle of operation for decomposing water by the hydrogen production apparatus shown in FIG. 4.
[図 6]図 6は、実施例及び比較例において使用した三電極系の実験装置の構成を示 す図である。  FIG. 6 is a diagram showing a configuration of a three-electrode experimental apparatus used in Examples and Comparative Examples.
[図 7]図 7は、実施例 4及び実施例 5において使用した Ή板を示す図であり、（a)は、 Ti 板の上面図であり、（b)は、（a)に示す Ti板の A—A'断面図である。  [FIG. 7] FIG. 7 is a view showing a steel plate used in Example 4 and Example 5, (a) is a top view of a Ti plate, and (b) is a Ti plate shown in (a). It is AA 'sectional drawing of a board.
[図 8]図 8は、実施例 1〜実施例 3及び比較例 1〜比較例 3につ 、ての光電流値の測 定結果を示すグラフである。  FIG. 8 is a graph showing the measurement results of the photocurrent values for Examples 1 to 3 and Comparative Examples 1 to 3.
[図 9]図 9は、実施例 4、実施例 5及び比較例 3についての光電流値の測定結果を示 すグラフである。  FIG. 9 is a graph showing the measurement results of photocurrent values for Example 4, Example 5, and Comparative Example 3.
[図 10]図 10は、実施例 6及び比較例 4についての光電流値の測定結果を示すグラフ である。  FIG. 10 is a graph showing the measurement results of photocurrent values for Example 6 and Comparative Example 4.
[図 11]図 11は、従来の半導体光電極を示す拡大断面図である。  FIG. 11 is an enlarged cross-sectional view showing a conventional semiconductor photoelectrode.
発明を実施するための最良の形態  BEST MODE FOR CARRYING OUT THE INVENTION
[0013] 本発明の実施の形態に係る半導体光電極、その製造方法及び半導体光電極を用[0013] A semiconductor photoelectrode according to an embodiment of the present invention, a manufacturing method thereof, and a semiconductor photoelectrode are used.
Vヽた光エネルギ変換装置にっ 、て説明する。 The V light energy converter will be explained.
[0014] (半導体光電極） [0014] (Semiconductor photoelectrode)
図 1では、本発明の実施の形態に係る半導体光電極 1の表面状態を示す。半導体 光電極 1は、表面に凹凸を作成して高表面積とした金属基板 2と、金属基板 2表面に 作成された半導体層 3と、を備える。  FIG. 1 shows the surface state of the semiconductor photoelectrode 1 according to the embodiment of the present invention. The semiconductor photoelectrode 1 includes a metal substrate 2 having a high surface area by forming irregularities on the surface, and a semiconductor layer 3 formed on the surface of the metal substrate 2.
[0015] 金属基板 2表面の凹凸は、できるだけ平均的に、かつ溝を深く作成することが好ま しい。具体的には、金属基板 2表面の算術平均粗さ（Ra)を 1 μ πι〜4 /ζ mの範囲とす ることが好ましい。この理由は、この範囲にすることで一層高い光電流値が得られるた めである。なお、金属基板 2表面の算術平均粗さ（Ra)は、粗さ計 (テンコール製アル ファステップ)を用いて、以下に示す数式から求めた値である。数式 1中の 1は基準長 さ、 x)は金属基板 2表面の形状の粗さに沿う曲線を示す。 [0015] It is preferable that the unevenness on the surface of the metal substrate 2 is formed on the average as much as possible and the groove is deep. Specifically, the arithmetic average roughness (Ra) of the surface of the metal substrate 2 is preferably in the range of 1 μπι to 4 / ζ m. The reason for this is that a higher photocurrent value can be obtained within this range. The arithmetic average roughness (Ra) of the surface of the metal substrate 2 is a value obtained from the following equation using a roughness meter (Tencor Alpha Step). In Equation 1, 1 is a reference length, and x) is a curve along the roughness of the shape of the metal substrate 2 surface.
[数 1] 1 c i , [Number 1] 1 c i,
Ra= - J ( x  Ra =-J (x
[0016] また、最大高さ（Ry)は、 1〜500 μ mの範囲とするのが好ましぐさらに 3〜200 μ m の範囲とすることが好ましい。ここで、最大高さ (Ry)とは、凹凸形状の平均線と最大 凸部の距離 (X)と、凹凸形状の平均面と最小凹部の距離 (y)との合計値 (x+y)を意 味する。なお本明細書にぉ 、て、算術平均粗さ（Ra)及び最大高さ（Ry)は、 JIS BO 601 (ISO 4287)に従!ヽ、求めること力できる。 [0016] The maximum height (Ry) is preferably in the range of 1 to 500 μm, and more preferably in the range of 3 to 200 μm. Here, the maximum height (Ry) is the total value (x + y) of the distance between the average line of the concavo-convex shape and the maximum convex portion (X) and the distance between the average surface of the concavo-convex shape and the minimum concave portion (y). Means. In this specification, the arithmetic average roughness (Ra) and the maximum height (Ry) can be determined according to JIS BO 601 (ISO 4287).
[0017] さらに凹凸の間隔は 500 μ m以下で、できるだけ緻密であることが望ましい。ここで 凹凸の間隔とは、図 2に示すように、表面の粗さ曲線 33において、隣接する凸部の 間隔 34を示す。なお図 2中の参照符号 32は、平均線を示す。  [0017] Further, it is desirable that the unevenness interval is 500 μm or less and is as dense as possible. Here, the interval between the projections and depressions indicates the interval 34 between adjacent projections in the surface roughness curve 33 as shown in FIG. Reference numeral 32 in FIG. 2 represents an average line.
[0018] 金属基板 2としては、元素の単体又はその元素の複合物（酸化物、窒化物、ホウィ匕 物、酸窒化物、硫化物、酸硫ィ匕物など）を用いることができる。これらの材料は、光触 媒特性又は光電極特性を示すことができる。具体的には、 Ti、 Nb、 Ta、 W、 V、 Co、 Fe 、Ni及び Inの中力 選択される少なくとも 1種以上の元素及びその複合物を金属基板 として用いることが好ましい。  [0018] As the metal substrate 2, a single element or a composite of the element (oxide, nitride, white nitride, oxynitride, sulfide, oxysulfide, etc.) can be used. These materials can exhibit photocatalytic properties or photoelectrode properties. Specifically, it is preferable to use, as the metal substrate, at least one element selected from among Ti, Nb, Ta, W, V, Co, Fe, Ni and In and a composite thereof.
[0019] 半導体層 3としては、光触媒作用を有する材料を用いることができる。具体的には、 TiO、 Nb 0、 Ta 0、 WO、 V 0、 InCuTaO、 InNiTaO、 InCoTaO、 InFeTaO、 InMn For the semiconductor layer 3, a material having a photocatalytic action can be used. Specifically, TiO, Nb 0, Ta 0, WO, V 0, InCuTaO, InNiTaO, InCoTaO, InFeTaO, InMn
2 2 5 2 5 3 2 5 4 4 4 42 2 5 2 5 3 2 5 4 4 4 4
TaO、 InTaO、 InNbTaO、 SrTiO、 TaONまたは TiO： N (窒素をドープしたチタ-ァ）TaO, InTaO, InNbTaO, SrTiO, TaON or TiO: N (nitrogen-doped titer)
4 4 4 3 2 4 4 4 3 2
を挙げることができる力 例示した材料に限定されるものではない。また半導体層 3の 材料は、金属基板 2を形成する金属の化合物と異なるようにしてもかまわな ヽ。  Forces that can be mentioned It is not limited to the exemplified materials. The material of the semiconductor layer 3 may be different from the metal compound forming the metal substrate 2.
[0020] 半導体層 3の厚さは、 0. 1 m〜l μ mの範囲とすることが好ましい。半導体層 3の 厚さが 0.： L m未満となり薄くなりすぎると、光の吸収効率が低下する。逆に、その厚 さ力 mを超えると電荷の移動距離が長くなるため、電荷の移動が遅くなつたり、電 荷が再結合してしまうからである。  [0020] The thickness of the semiconductor layer 3 is preferably in the range of 0.1 m to l μm. If the thickness of the semiconductor layer 3 is less than 0 .: L m and becomes too thin, the light absorption efficiency decreases. On the other hand, if the thickness force m is exceeded, the charge transfer distance becomes long, so that the charge transfer becomes slow or the charges are recombined.
[0021] このように半導体光電極 1の表面に凹凸を作成すると、入射光 4だけでなく散乱光 5 をも半導体層 3により吸収することができる。このため、半導体層 3の厚さを薄くしても 光の吸収効率が低下することはない。また、半導体層 3の厚さを薄くすると、電荷の移 動距離が短くなり、電荷はすぐに金属基板 2に到達する。金属基板 2中の抵抗は小さ いため、電荷は金属基板 2内を高速で移動することになる。また、従来の電極に比べ て、半導体層 3の実質的な表面積が広くなるため、半導体層 3中の電荷密度を低くす ることができる。この結果、半導体層 3での電荷の再結合を防止することができる。 When irregularities are created on the surface of the semiconductor photoelectrode 1 in this way, not only the incident light 4 but also the scattered light 5 can be absorbed by the semiconductor layer 3. For this reason, even if the thickness of the semiconductor layer 3 is reduced, The light absorption efficiency does not decrease. In addition, when the thickness of the semiconductor layer 3 is reduced, the charge transfer distance is shortened, and the charge immediately reaches the metal substrate 2. Since the resistance in the metal substrate 2 is small, the charge moves in the metal substrate 2 at a high speed. In addition, since the substantial surface area of the semiconductor layer 3 is larger than that of the conventional electrode, the charge density in the semiconductor layer 3 can be reduced. As a result, charge recombination in the semiconductor layer 3 can be prevented.
[0022] (半導体光電極の製造方法）  [0022] (Method for Manufacturing Semiconductor Photoelectrode)
次に、本発明の実施の形態に係る半導体光電極の製造方法を説明する。  Next, a method for manufacturing a semiconductor photoelectrode according to an embodiment of the present invention will be described.
[0023] まず、表面に凹凸を有する金属基板 2を作成する。凹凸の作成法としては、金属板 を機械的研磨した後、化学エッチング処理をする方法を用いることができる。この時、 最大高さ（Ry)は 1 μ m〜500 μ m、さらに 3 μ m〜200 μ mとすることが好ましぐまた 、凹凸の間隔は 500 m以下として、凹凸の間隔を狭くすることが好ましい。また凹凸 の作成法としては、金属板を研磨紙等を用いて粗研磨することにより作成しても良い  [0023] First, the metal substrate 2 having irregularities on the surface is prepared. As a method for forming the unevenness, a method of performing chemical etching after mechanically polishing the metal plate can be used. At this time, the maximum height (Ry) is preferably 1 μm to 500 μm, and more preferably 3 μm to 200 μm. Also, the unevenness interval is set to 500 m or less to narrow the unevenness interval. It is preferable. Further, as a method of creating the unevenness, the metal plate may be prepared by rough polishing using a polishing paper or the like.
[0024] また金属基板 2としては、図 3に示すように、金属粒子 36を圧力または熱により接合 することにより成る、表面に凹凸を有する多孔質体を用いることもできる。この時に使 用する金属粒子 36の粒径 (D50)は 1 m〜400 μ m、好ましくは 3 μ m〜200 μ m の範囲とすることが好ましい。なお、接合する際の圧力や熱は、金属粒子の種類や粒 径に応じて変えることが好ま 、。このように圧力や熱により金属粒子を接合すると、 金属粒子間の界面のネッキング成長が進行して電気的な接触が良くなり、さらに機 械的強度に優れた金属基板 35とすることができる。なお図 3の金属基板 35は、金属 粒子 36が縦横とも整然と配列されているが、本発明の金属基板はこれに限らず、金 属粒子を圧力または熱により接合することにより成る、あらゆる多孔質体を用いること ができる。 As the metal substrate 2, as shown in FIG. 3, a porous body having irregularities on the surface formed by joining metal particles 36 by pressure or heat can also be used. The particle size (D50) of the metal particles 36 used at this time is preferably in the range of 1 m to 400 μm, preferably 3 μm to 200 μm. In addition, it is preferable to change the pressure and heat at the time of joining according to the type and particle size of the metal particles. When the metal particles are bonded together by pressure or heat in this manner, the necking growth at the interface between the metal particles proceeds to improve the electrical contact, and the metal substrate 35 having excellent mechanical strength can be obtained. Note that the metal substrate 35 in FIG. 3 has the metal particles 36 arranged in an orderly manner both vertically and horizontally. However, the metal substrate of the present invention is not limited to this, and any porous material formed by joining metal particles by pressure or heat. The body can be used.
[0025] なお、粒子の大きさを測定するものとして、大きさの分布 (範囲と含有率)を測定す る粒度分布がある。粒度分布は、一般には目開きの異なるいくつかのふるいを用い て、その目開きを通過する割合を測定し、（積算)重量百分率で表す。本発明で用い る金属粒子は、数/ z mレベルのため、一般の粒度分布計を用いて測定し、積算値 50 %の粒度を「粒径 (D50)」とする。 [0026] 次に、得られた金属基板 2上に半導体層 3を作成するが、半導体層 3は使用する原 材料に応じてその製造方法が異なる。 [0025] Incidentally, as a method for measuring the size of particles, there is a particle size distribution for measuring the size distribution (range and content). The particle size distribution is generally expressed as a (percentage) weight percentage by using several sieves with different openings and measuring the percentage passing through the openings. Since the metal particles used in the present invention are several / zm level, they are measured using a general particle size distribution meter, and the particle size having an integrated value of 50% is defined as “particle size (D50)”. Next, the semiconductor layer 3 is formed on the obtained metal substrate 2, and the manufacturing method of the semiconductor layer 3 differs depending on the raw material used.
[0027] 半導体層 3が単純酸ィ匕物力も成る場合には、酸化雰囲気下 (空気中、酸素中）にお V、て、単純金属から成る金属基板を焼成あるいは電解酸化する。  [0027] When the semiconductor layer 3 also has simple acidity and physical strength, a metal substrate made of a simple metal is baked or electrolytically oxidized in an oxidizing atmosphere (in air or oxygen).
[0028] 半導体層 3が単純金属の窒化物若しくは硫ィ匕物力 成る場合には、非酸化雰囲気 下 (アンモニア、窒素、硫化水素など）において、単純金属から成る金属基板を加熱 あるいはプラズマ処理をする。例えば Ta5+、 Ti4+などの d型の電子配置を有する遷移 金属イオンを含むォキシナイトライド (例えば、 TaON)、窒素をドープした半導体 (例え ば、 ΉΟ： N)、ォキシサルファイドなど力も成る半導体層 3の場合には、単純金属から[0028] When the semiconductor layer 3 has a simple metal nitride or sulfide strength, the metal substrate made of the simple metal is heated or plasma-treated in a non-oxidizing atmosphere (ammonia, nitrogen, hydrogen sulfide, etc.). . For example, oxynitrides containing transition metal ions with a d-type electron configuration such as Ta 5+ and Ti 4+ (eg TaON), nitrogen-doped semiconductors (eg ΉΟ: N), oxysulfide, etc. In the case of the semiconductor layer 3 which also has a force, from a simple metal
2 2
成る金属基板を一度部分酸化した後に窒化処理あるいは硫化処理をするか、又は 窒化処理あるいは硫化処理をした後に部分酸化することにより得られる。  It is obtained by partially oxidizing the metal substrate once and then performing nitriding treatment or sulfiding treatment, or by performing partial oxidization after nitriding treatment or sulfiding treatment.
[0029] 半導体層 3が複合金属半導体から成る場合には、金属基板 2上に複合金属前駆体 を塗布し、その後、酸化、窒化又は硫ィ匕のいずれかの処理を行い、半導体層 3を作 成する。 [0029] When the semiconductor layer 3 is composed of a composite metal semiconductor, a composite metal precursor is applied onto the metal substrate 2, and then any one of oxidation, nitridation, and sulfur treatment is performed to form the semiconductor layer 3. create.
[0030] 上記半導体層 3を作成した後、後処理として、酸化、水素還元、水蒸気によって処 理をしてもよい。後処理をすると半導体層 3中の格子欠陥を減少あるいは増やすこと ができる。なお、半導体層 3中の格子欠陥を増やすと導電性が高くなる。  [0030] After the semiconductor layer 3 is formed, post treatment may be performed by oxidation, hydrogen reduction, or steam. Post-processing can reduce or increase lattice defects in the semiconductor layer 3. Note that increasing the number of lattice defects in the semiconductor layer 3 increases the conductivity.
[0031] (水素製造装置）  [0031] (Hydrogen production equipment)
本発明の半導体光電極を用いた水素製造装置 6の構成を図 4に示す。水素製造 装置 6では、水槽 7内に半導体光電極 8 (作用極）と対極 9 (例えば、 Pt電極、カーボ ン電極)とを個別に配置し、さらに半導体光電極 8と対極 9を配置した水槽 7の中間位 置にイオン交換膜 12を取り付けている。さらに半導体光電極 8と対極 9に導線を接続 することにより外部短絡線 10を作成する。また、水槽 7内には電解反応の溶液抵抗を 下げるために安定な支持電解質を含む電解液 11 (例えば、 Na SO水溶液)を貯留し  FIG. 4 shows the configuration of a hydrogen production apparatus 6 using the semiconductor photoelectrode of the present invention. In the hydrogen production device 6, a semiconductor photoelectrode 8 (working electrode) and a counter electrode 9 (for example, a Pt electrode and a carbon electrode) are individually arranged in a water tank 7, and a semiconductor photoelectrode 8 and a counter electrode 9 are further arranged. An ion exchange membrane 12 is attached to the middle position of 7. Furthermore, an external short-circuit wire 10 is created by connecting a conductor to the semiconductor photoelectrode 8 and the counter electrode 9. In addition, in the water tank 7, an electrolyte solution 11 (for example, Na SO aqueous solution) containing a stable supporting electrolyte is stored in order to reduce the solution resistance of the electrolytic reaction.
2 4  twenty four
ている。本構成の水素製造装置 6では、半導体光電極 8に太陽光 13を照射して水の 電解を行う。  ing. In the hydrogen production apparatus 6 having this configuration, the semiconductor photoelectrode 8 is irradiated with sunlight 13 to electrolyze water.
[0032] 対極 9の材料は、反応に合わせたものを選択することができる。水素を発生させるた めには、水素発生の過電圧の低い Pt電極及びカーボン電極が有効である力 安価 な Co-Mo電極を用いても良い。支持電解質としては、一般的な電解反応の電解質と して使用される NaOH、 Na SO、 H SO及び Na HPOを用いることができる。支持電解 [0032] The material of the counter electrode 9 can be selected according to the reaction. In order to generate hydrogen, Pt electrode and carbon electrode with low hydrogen overvoltage are effective. Any Co-Mo electrode may be used. As the supporting electrolyte, NaOH, Na 2 SO 4, H 2 SO 4 and Na 2 HPO which are used as electrolytes for general electrolytic reactions can be used. Supporting electrolysis
2 4 2 4 2 4  2 4 2 4 2 4
質の濃度は、電解の過電圧を低下させるために高濃度にすると良ぐ 0. Olmol/L 以上とすることが好ましい。また、光触媒が容易に分解できる還元性の反応物 (例え ば、有機物、硫化水素、ヨウ素イオン)を電解液 11中に含有させても良ぐこれにより 光電変換効率が高めることができる。特に、本願発明のように金属基板に凹凸を設け ると、光触媒 (半導体層）と反応基質との反応面積が広くなるため、光散乱の影響を 受けにくくなる。このため、従来の電極に比べて飛躍的に光電変換効率が高くなる。 なお、図 4には図示しないが、外部短絡線 10にポテンシヨスタツト又はソースメータを 設置してバイアス電位を制御しても良い。また、電極の性能をチェックする場合ゃ特 殊な化学反応を起こす場合には、太陽光 13ではなく人工光源 (例えば、キセノンラン プ）を適用しても良い。  The concentration of the material should be higher than 0. Olmol / L in order to reduce the overvoltage of electrolysis. In addition, a reducing reactant that can be easily decomposed by the photocatalyst (for example, an organic substance, hydrogen sulfide, or iodine ion) may be contained in the electrolyte solution 11. This can increase the photoelectric conversion efficiency. In particular, when the metal substrate is provided with irregularities as in the present invention, the reaction area between the photocatalyst (semiconductor layer) and the reaction substrate is widened, so that it is less susceptible to light scattering. For this reason, the photoelectric conversion efficiency is remarkably increased as compared with the conventional electrode. Although not shown in FIG. 4, a bias potential or a source meter may be installed on the external short-circuit line 10 to control the bias potential. In addition, when checking the performance of the electrode and causing a special chemical reaction, an artificial light source (for example, a xenon lamp) may be applied instead of the sunlight 13.
[0033] 次に、図 4に示した水素製造装置 6により水を分解する動作原理を図 5により説明 する。半導体光電極 8に太陽光 13を照射すると、図 5に示すように、半導体光電極 8 に光が吸収されて、伝導帯に電子 16が生成し、価電子帯に正孔 14が生成する。半 導体光電極 8の表面に移動した正孔 14は、式 1に示す反応により、水を酸化して酸 素 15を生成する。  Next, the operation principle of decomposing water by the hydrogen production apparatus 6 shown in FIG. 4 will be described with reference to FIG. As shown in FIG. 5, when the semiconductor photoelectrode 8 is irradiated with sunlight 13, the semiconductor photoelectrode 8 absorbs light, generating electrons 16 in the conduction band and holes 14 in the valence band. The holes 14 transferred to the surface of the semiconductor photoelectrode 8 oxidize water by the reaction shown in Equation 1 to generate oxygen 15.
[0034] H 0→2H+ + l/20 + 2e" (式 1) [0034] H 0 → 2H + + l / 20 + 2e "(Formula 1)
2 2  twenty two
一方、生成した電子 16は、半導体光電極 8中の金属基板 2に移動した後、外部短 絡線 10を通り対極 9に移動する。この電子（e_)は、対極 9上で水を還元し、式 2に示 す反応により、水素 17を生成する。  On the other hand, the generated electrons 16 move to the metal substrate 2 in the semiconductor photoelectrode 8, and then move to the counter electrode 9 through the external short line 10. This electron (e_) reduces water on the counter electrode 9 and generates hydrogen 17 by the reaction shown in Equation 2.
[0035] 2H + 2e"→H (式 2) [0035] 2H + 2e "→ H (Formula 2)
2  2
この結果、水が分解されて、半導体光電極 8 (作用極)では水素、対極 9では酸素が それぞれ生成する。  As a result, water is decomposed to generate hydrogen at the semiconductor photoelectrode 8 (working electrode) and oxygen at the counter electrode 9.
[0036] なお、ここでは、本発明の実施の形態に係る半導体光電極を用いて水素製造装置 6を構成した例を挙げたが、半導体光電極は水電解装置に限定されず、色素増感型 太陽電池などの光エネルギ変換装置として適用することもできる。  Here, an example in which the hydrogen production apparatus 6 is configured using the semiconductor photoelectrode according to the embodiment of the present invention has been described, but the semiconductor photoelectrode is not limited to the water electrolysis apparatus, and is dye-sensitized. It can also be applied as a light energy conversion device such as a type solar cell.
[0037] 以下、実施例を用いてさらに具体的に説明する。各実施例では、異なる製造方法 を用いて製造した、異なる構成の半導体光電極を用いて、図 6に示す三電極系の実 験装置に適用した実験を行った。図 6に示す三電極系の実験装置 18は、水槽 19内 に、作用極である半導体光電極 20と、対極である Pt電極 21とを配置し、半導体光電 極 20と Pt電極 21とに外部短絡線 22を接続して導通させている。また、別の水槽 23 内に、作用極の電位を設定及び制御するための基準電極となる参照極を配置してお り、この参照極として銀-塩化銀電極 (Ag-AgCl電極） 24を用いている。 2つの水槽 19 ,23はバイコールガラスフリット 25により接続されて、半導体光電極 20と Pt電極 21と の間の電気的な導通を保っている。半導体光電極 20と Pt電極 21とを接続する外部 短絡線 22には電流計 26を設置し、回路を流れる光電流値を計測している。さらに、 外部短絡線 22にポテンシヨスタツト 27を設置し、ポテンシヨスタツト 27と Ag-AgCl電極 24とを外部短絡線 28により接続している。ポテンシヨスタツト 27は、電位に応じて電 流を流し、半導体光電極 20と Ag-AgCl電極 24との間の電位差をコントロールして!/ヽ る。水槽 19内には、濃度 0. lmol/Lの Na SO水溶液を貯留している。この Na SO水 [0037] Hereinafter, the present invention will be described in more detail using examples. In each embodiment, a different manufacturing method Using a semiconductor photoelectrode with a different configuration manufactured using, an experiment applied to the three-electrode system experimental device shown in Fig. 6 was conducted. A three-electrode experimental apparatus 18 shown in FIG. 6 has a semiconductor photoelectrode 20 as a working electrode and a Pt electrode 21 as a counter electrode disposed in a water tank 19, and the semiconductor photoelectrode 20 and the Pt electrode 21 are externally connected. The short-circuit wire 22 is connected and made conductive. In addition, a reference electrode serving as a reference electrode for setting and controlling the potential of the working electrode is disposed in another water tank 23, and a silver-silver chloride electrode (Ag-AgCl electrode) 24 is provided as the reference electrode. Used. The two water tanks 19 and 23 are connected by a Vycor glass frit 25 to maintain electrical continuity between the semiconductor photoelectrode 20 and the Pt electrode 21. An ammeter 26 is installed on the external short-circuit line 22 connecting the semiconductor photoelectrode 20 and the Pt electrode 21 to measure the photocurrent value flowing through the circuit. Further, a potentiostat 27 is installed on the external short-circuit wire 22, and the potentiostat 27 and the Ag-AgCl electrode 24 are connected by the external short-circuit wire 28. The potentiostat 27 controls the potential difference between the semiconductor photoelectrode 20 and the Ag-AgCl electrode 24 by passing a current according to the potential. In the water tank 19, an Na SO aqueous solution having a concentration of 0.1 mol / L is stored. This Na SO water
2 4 2 4 溶液は、半導体光電極 20と Pt電極 21とに電位差が生じた場合に回路中の電荷移動 を担う役割を果たしている。  The 2 4 2 4 solution plays a role in charge transfer in the circuit when a potential difference occurs between the semiconductor photoelectrode 20 and the Pt electrode 21.
[0038] 半導体光電極 20が配置された水槽 19の外部には、キセノンランプ（500W) 29を 配置し、キセノンランプ 29と半導体光電極 20との間にチヨッパ 30を設置している。チ ョッパ 30により半導体光電極 20に照射する光の ON、 OFFを一定間隔で切り替えて いる。 A xenon lamp (500 W) 29 is disposed outside the water tank 19 in which the semiconductor photoelectrode 20 is disposed, and a chopper 30 is disposed between the xenon lamp 29 and the semiconductor photoelectrode 20. The light applied to the semiconductor photoelectrode 20 by the chopper 30 is switched at regular intervals.
[0039] (実施例 1〜実施例 3)  (Example 1 to Example 3)
実施例 1〜実施例 3では、金属基板 2として、平均粒径 45 mの Ti金属粒子を加熱 及び加圧することによりネッキングして作成した Ti多孔質体を使用した。 Ti多孔質体 の算術平均粗さ（Ra)は約 2 μ mであり、最大高さ（Ry)は約 5 μ mであった。  In Examples 1 to 3, a Ti porous body prepared by necking Ti metal particles having an average particle diameter of 45 m by heating and pressing was used as the metal substrate 2. The arithmetic average roughness (Ra) of the porous Ti material was about 2 μm, and the maximum height (Ry) was about 5 μm.
[0040] この Ti多孔質体を空気雰囲気下において 500°C〜700°Cの範囲で温度を変えて、 1時間熱処理をした。熱処理温度として、実施例 1では 500°C、実施例 2では 600°C 、実施例 3では 700°Cとした。熱処理により Ti多孔質体表面を酸化して TiO層を作成  [0040] This Ti porous body was heat-treated for 1 hour in an air atmosphere while changing the temperature in the range of 500 ° C to 700 ° C. The heat treatment temperature was 500 ° C in Example 1, 600 ° C in Example 2, and 700 ° C in Example 3. The surface of the porous Ti body is oxidized by heat treatment to create a TiO layer.
2 した。  2
[0041] X線回折 (XRD)により構造を同定したところ、 TiOはルチル型であることが判明し た。また、断面 SEM分析の結果から、熱処理温度が高くなるに従い、 TiO層の厚さ [0041] When the structure was identified by X-ray diffraction (XRD), TiO was found to be rutile. It was. From the results of cross-sectional SEM analysis, as the heat treatment temperature increases,
2 が増大していた。 TiO層の厚さは、測定場所に応じてばらつきがあるものの、実施例  2 was increasing. The thickness of the TiO layer varies depending on the measurement location.
2  2
1は 100nm、実施例 2は 200nm、実施例 3は 600 mであった。  1 was 100 nm, Example 2 was 200 nm, and Example 3 was 600 m.
[0042] (比較例 1〜比較例 3) [0042] (Comparative Example 1 to Comparative Example 3)
比較例 1〜比較例 3では、実施例 1〜実施例 3により使用した Ti多孔質体に替えて Ti平板を用いた。 Ti平板の算術平均粗さ（Ra)は 0. 2 μ m〜0. 3 μ mであった。また Ti平板表面には大きな凹凸が作成されず、最大高さ（Ry)は 1 μ m未満であった。な お、 Ti平板を使用した以外は、実施例 1〜実施例 3に示した製造方法と同様の方法 を用いて、半導体光電極を製造した。 TiO層の厚さは、測定場所に応じてばらつき  In Comparative Examples 1 to 3, a Ti flat plate was used in place of the Ti porous body used in Examples 1 to 3. The arithmetic average roughness (Ra) of the Ti flat plate was 0.2 μm to 0.3 μm. Moreover, no large irregularities were created on the surface of the Ti plate, and the maximum height (Ry) was less than 1 μm. A semiconductor photoelectrode was manufactured using a method similar to the manufacturing method shown in Examples 1 to 3 except that a Ti flat plate was used. The thickness of the TiO layer varies depending on the measurement location
2  2
があるが、比較例 1は 100nm、比較例 2は 200nm、比較例 3は 600 mであった。  However, Comparative Example 1 was 100 nm, Comparative Example 2 was 200 nm, and Comparative Example 3 was 600 m.
[0043] (実施例 4、実施例 5) [0043] (Example 4, Example 5)
実施例 4、実施例 5では、金属基板 2として、 Ti平板をフォトレジストマスクにてパタ ーンユングしたものをエッチング処理して、表面に凹凸を作成した Ti板 31を使用した 。 Ti板の表面は、図 7 (a)に示す形状とした。また、図 7 (a)に示す Ti板表面の A— A' 断面図を図 7(b)に示した。実施例 4では、図 7(b)に示す X, Yをそれぞれに 5 m, 7 0 mとし、実施例 5では、 X, Yをそれぞれ 40 m, 70 mとした。実施例 4及び実 施例 5の Ή板の算術平均粗さ（Ra)を測定したところ、実施例 4は 3. O ^ m,実施例 5 は 3. 3 ！11で&)った。  In Example 4 and Example 5, as the metal substrate 2, a Ti plate 31 in which a Ti flat plate was patterned with a photoresist mask and etched to create irregularities on the surface was used. The surface of the Ti plate had the shape shown in Fig. 7 (a). Fig. 7 (b) shows the AA 'cross section of the Ti plate surface shown in Fig. 7 (a). In Example 4, X and Y shown in FIG. 7 (b) were 5 m and 70 m, respectively, and in Example 5, X and Y were 40 m and 70 m, respectively. When the arithmetic mean roughness (Ra) of the slats of Example 4 and Example 5 was measured, Example 4 was 3. O ^ m, Example 5 was 3.3! 11 &).
[0044] 得られた Ti板を、空気雰囲気下にて 700°Cの温度で 1時間熱処理し、 Ti板表面を 酸化して TiO層を作成した。 TiO層の厚さは、測定場所に応じてばらつきがあるが、  [0044] The obtained Ti plate was heat-treated at 700 ° C for 1 hour in an air atmosphere to oxidize the Ti plate surface to form a TiO layer. The thickness of the TiO layer varies depending on the measurement location,
2 2  twenty two
実施 f列 4ίま 600 μ m、実施 f列 5ίま 600 μ mであった。  The implementation f row was 4 μm up to 600 μm, and the implementation f row 5 up to 600 μm.
[0045] (実施例 6) [0045] (Example 6)
実施例 6では、まず WOの水和コロイドを調製した。 WOの水和コロイドは、イオン  In Example 6, first, a hydrated colloid of WO was prepared. WO hydrate colloids are ions
3 3  3 3
交換榭脂を用いて Na WO水溶液中の Na+イオンをプロトン交換することにより調製し  Prepared by exchanging Na + ions in Na WO aqueous solution using proton exchange resin.
2 4  twenty four
た。この水和コロイド水溶液を等量エタノールと混合した後、減圧蒸留（60°C)して、 その体積を 1/4に減少させた。その後、 1/2量のポリエチレングリコール 300 (和光 純薬製)を加えてスターラを用いて混合し、 WOをコロイド状としたスラリーを得た。  It was. This hydrated colloidal aqueous solution was mixed with an equal volume of ethanol and then distilled under reduced pressure (60 ° C) to reduce its volume to 1/4. Thereafter, 1/2 amount of polyethylene glycol 300 (manufactured by Wako Pure Chemical Industries, Ltd.) was added and mixed using a stirrer to obtain a colloidal slurry of WO.
3  Three
[0046] 得られたスラリーを実施例 1で使用した Ti多孔質体上に塗布した後、 500°Cで 1時 間熱処理することにより、 Ti多孔質体上に WO層を作成した。なお WO層は粒子の [0046] After applying the obtained slurry onto the Ti porous body used in Example 1, it was 1 hour at 500 ° C. A WO layer was formed on the Ti porous body by performing an intermediate heat treatment. The WO layer is made up of particles
3 3  3 3
集合体で凹凸はあるが一様の厚さでないため層厚は測定できな力つた。  The assemblage was uneven, but the layer thickness was not uniform, so the layer thickness was not measurable.
[0047] (比較例 4)  [0047] (Comparative Example 4)
比較例 4では、実施例 6により製造したスラリーを用いて、このスラリーを比較例 1で 使用した Ti平板上に塗布した後、 500°Cで 1時間熱処理をして、 Ti平板上に WO層を  In Comparative Example 4, using the slurry produced in Example 6, this slurry was applied on the Ti flat plate used in Comparative Example 1, and then heat-treated at 500 ° C. for 1 hour to form a WO layer on the Ti flat plate. The
3 作成した。なお WO層は粒子の集合体で凹凸はあるが一様の厚さでないため層厚は  3 Created. Note that the WO layer is an aggregate of particles with irregularities but not a uniform thickness.
3  Three
測定できな力つた。  I couldn't measure it.
[0048] 実施例 1〜実施例 6及び比較例 1〜比較例 4の各半導体光電極について、光電流 測定試験により光電流値を測定した。測定結果を表 1に示す。  For each semiconductor photoelectrode of Examples 1 to 6 and Comparative Examples 1 to 4, photocurrent values were measured by a photocurrent measurement test. Table 1 shows the measurement results.
[表 1] 金属基板 半導体層  [Table 1] Metal substrate Semiconductor layer
光電流値 算術平均粗さ ( Ra) 最大高さ （Ry) 厚さ ( μ A ) ( μ m ) m ) V μ m )  Photocurrent value Arithmetic mean roughness (Ra) Maximum height (Ry) Thickness (μA) (μm) m) V μm)
実施例 1 2 . 0 5 . 0 0 . 1 1 2 0 実施例 2 2 . 0 5 . 0 . 2 3 2 0 実施例 3 2 . 0 5 . 0 . 6 4 0 0 実施例 4 3 . 0 1 0 . 0 0 . 6 3 0 0 実施例 5 3 . 3 8 . 8 0 . 6 3 2 0 比較例 1 0 . 2 ^ 0 . 3 1未満 0 . 1 8 0 比較例 2 0 . 2 - 0 . 3 1未満 0 . 2 9 5 比較例 3 0 . 2 ^ 0 . 3 1未満 0 . 6 1 4 0 実施例 6 2 . 0 5 . ― 5 5 0 比較例 4 0 . 2 ' ^ 0 . 3 1未満 ― 3 1 0  Example 1 2 .0 5 .0 0 .1 1 2 0 Example 2 2 .5 5 .0 .2 3 2 0 Example 3 2 .0 5 .0 .6 4 0 0 Example 4 3. 0 1 0 5 .6 3 0 0 Example 5 3 .3 8 .8 0 .6 3 2 0 Comparative Example 1 <0.2 ^ <0.3 1 Less than 0.1 8 0 Comparative Example 2 0.2-0. 3 Less than 1 0.2 9 5 Comparative Example 3 0.2 ^ 0. 3 Less than 1 0.6 1 4 0 Example 6 2 0 5 .- 5 5 0 Comparative Example 4 0.2 '^ 0. 3 1 Less than-3 1 0
[0049] なお、光電流測定試験は、参照極に対する半導体光電極の電位を 0.05 V/sの操 作速度で変化させるポテンシャルスイープ法を用いた。この結果、半導体光電極に 光を照射した場合のみ、 Ag/AgCl基準で 0 V付近カゝら水の分解に伴う光電流が確認 された。なお、以下、電位は Ag/AgClを基準として標記する。 In the photocurrent measurement test, a potential sweep method was used in which the potential of the semiconductor photoelectrode with respect to the reference electrode was changed at an operation speed of 0.05 V / s. As a result, only when the semiconductor photoelectrode was irradiated with light, a photocurrent accompanying water decomposition near 0 V was confirmed based on Ag / AgCl. In the following, the potential is indicated based on Ag / AgCl.
[0050] 光電流値を測定したところ、電圧が貴になるに伴い光電流値の値は徐々に増加し ていた。実施例 1〜実施例 3及び比較例 1〜比較例 3について、 0.8 Vとして光電流 値を測定した結果を図 8に示す。図 8に示すように、実施例及び比較例の両者ともに 、熱処理温度が高くなるに伴い ΉΟ層が厚くなるため、光吸収特性が高まり、光電流 [0050] When the photocurrent value was measured, the photocurrent value gradually increased as the voltage became noble. For Example 1 to Example 3 and Comparative Example 1 to Comparative Example 3, the photocurrent was 0.8 V Figure 8 shows the measurement results. As shown in FIG. 8, in both the example and the comparative example, as the heat treatment temperature is increased, the soot layer becomes thicker, so that the light absorption characteristics are improved and the photocurrent is increased.
2  2
値が増大することが判明した。また、同一温度で熱処理した場合には、比較例に比 ベて実施例の光電流値は、いずれも約 1. 5倍〜 3. 0倍の高い光電流値を示してい た。これは、 Ti平板を使用した比較例 1〜比較例 3に比べて、 Ti多孔質体を使用した 実施例 1〜実施例 3では、半導体光電極表面に凹凸が作成されているため、散乱光 をも吸収することができるからである。また、半導体層の実質的な表面積を広げ、半 導体層中の電荷密度を低くすることにより、電荷の再結合を防ぐこともできるからであ る。さら〖こ、電子は半導体層よりも金属基板中を移動すると、抵抗が小さく有利である ため、金属基板を大面積化すると、半導体層から金属基板までの電荷の移動距離を 短くできる力 である。  The value was found to increase. In addition, when the heat treatment was performed at the same temperature, the photocurrent values of the examples were about 1.5 to 3.0 times higher than those of the comparative example. Compared with Comparative Examples 1 to 3 using a Ti flat plate, in Example 1 to Example 3 using a porous Ti material, unevenness was created on the surface of the semiconductor photoelectrode. It is because it can also absorb. Further, it is possible to prevent charge recombination by increasing the substantial surface area of the semiconductor layer and lowering the charge density in the semiconductor layer. Furthermore, when electrons move through the metal substrate rather than the semiconductor layer, the resistance is small and advantageous. Therefore, increasing the area of the metal substrate is a force that can shorten the distance of charge transfer from the semiconductor layer to the metal substrate. .
[0051] 次に、実施例 4、実施例 5及び比較例 3につ 、て、光電流値を測定した結果を図 9 に示す。図 9に示すように、表面に凹凸を作成した Ή板を使用した実施例 4及び実施 例 5は、 Ti平板を使用した比較例 3に比べて、光電流値は約 2倍増加していることが 判明しており、前述した実施例 1〜実施例 3と同様に、金属基板に凹凸を設けること が有効な手段であることが示された。  Next, for Example 4, Example 5, and Comparative Example 3, the results of measuring the photocurrent value are shown in FIG. As shown in Fig. 9, the photocurrent values of Example 4 and Example 5 using a plate with irregularities on the surface increased by about 2 times compared to Comparative Example 3 using a Ti flat plate. It was proved that, as in Examples 1 to 3 described above, it is effective to provide unevenness on the metal substrate.
[0052] さらに、実施例 6及び比較例 4について、光電流値を測定した結果を図 10に示す。  Furthermore, the results of measuring the photocurrent values for Example 6 and Comparative Example 4 are shown in FIG.
なお、実施例 6及び比較例 4では、 WOの光吸収特性のみを切り分けて考えるため  In Example 6 and Comparative Example 4, only the light absorption characteristics of WO are considered separately.
3  Three
に、 TiOの光吸収波長ではなぐ WOの光吸収波長である 420nm以上の光のみを In addition, only the light of 420 nm or more, which is the light absorption wavelength of WO, is not the light absorption wavelength of TiO.
2 3 twenty three
照射して、光電流値を測定した結果を示す。図 10に示すように、多孔質体を用いた 実施例 6の方が平板を用いた比較例 4に対して光電流値が約 1. 8倍であり、多孔質 体と平板とで有意な差が現れた。表面に凹凸を作成した半導体光電極は、表面を平 坦とした半導体光電極に比べて光吸収特性が良いという事実は、金属基板を酸ィ匕し て得た金属酸ィ匕物を光触媒とする光電極のみではなぐ凹凸を作成した金属基板上 にその金属の酸ィ匕物とは異なる光触媒を作成した場合でも成り立つことが判明した。  The result of measuring the photocurrent value after irradiation is shown. As shown in Fig. 10, the photocurrent value of Example 6 using a porous material is approximately 1.8 times that of Comparative Example 4 using a flat plate, which is significant between the porous material and the flat plate. A difference appeared. The fact that semiconductor photoelectrodes with irregularities on the surface have better light absorption characteristics than semiconductor photoelectrodes with a flat surface is the fact that metal oxides obtained by oxidizing a metal substrate are used as photocatalysts. It was found that this was true even when a photocatalyst different from the metal oxide was produced on a metal substrate on which irregularities were created that were not only the photoelectrode.
[0053] 以上、本発明の詳細について述べてきたが、本発明の思想に合致するものであれ ば、これらの構成及び文言に限定されるものではない。例えば、実施例 1では、 Ti多 孔質体を焼結したものを基板として使用したが、平板上に Ti多孔質体を作成して最 表面に凹凸を形成した半導体光電極を用いても良い。また、本発明の実施の形態で は、金属基板上に光触媒を担持する方法として、ペースト状とした光触媒を金属基板 上に塗布した後、熱処理をする方法を示したが、この方法に限定されず、物理蒸着 法または化学蒸着法を用いて、金属基板上に光触媒を担持しても良い。 [0053] The details of the present invention have been described above, but the present invention is not limited to these configurations and words as long as they are consistent with the idea of the present invention. For example, in Example 1, a sintered Ti porous body was used as a substrate. You may use the semiconductor photoelectrode which formed the unevenness | corrugation in the surface. In the embodiment of the present invention, as a method of supporting the photocatalyst on the metal substrate, a method of applying a heat treatment after applying the paste-like photocatalyst on the metal substrate has been shown. However, the present invention is not limited to this method. Alternatively, the photocatalyst may be supported on the metal substrate by physical vapor deposition or chemical vapor deposition.
[0054] さらに、図 4に示した水素製造装置 6では、半導体光電極 8と対極 9との間に電位を 印加するデバイスを設置していない。しかし外部短絡線 10上に電圧印加用のデバィ スを設置した構成としても良ぐまた、 2つの水槽 7間で pHの差をつけて濃度のバイ ァスをかける構成としても良!、。  Furthermore, in the hydrogen production apparatus 6 shown in FIG. 4, no device for applying a potential is installed between the semiconductor photoelectrode 8 and the counter electrode 9. However, a configuration in which a voltage application device is installed on the external short-circuit line 10 is also possible, and a configuration in which a pH difference is applied between the two tanks 7 to apply a concentration bias is also possible!
[0055] また、本発明ではホールにより酸ィ匕される物質として水を例に挙げた力 酸化される 物質は水に限定されず、例えば、工場廃水など有機物を含む電解質を用いてその 有機物を犠牲試薬として酸化することも考えられる。さらに実施例 4及び実施例 5で は、表面に凹凸を作成する方法として化学エッチング法を挙げたが、これに限定され ず、イオンエッチング、 LIGAプロセス若しくは陽極酸ィ匕により、表面に凹凸を作成し ても良い。  [0055] Further, in the present invention, the substance that can be oxidized by using water as an example of a substance that is oxidized by holes is not limited to water. For example, an organic substance such as factory waste water is used to convert the organic substance into an organic substance. Oxidation as a sacrificial reagent is also conceivable. Furthermore, in Example 4 and Example 5, the chemical etching method was mentioned as a method for creating irregularities on the surface, but the present invention is not limited to this, and irregularities are created on the surface by ion etching, LIGA process or anodizing. You can do it.
産業上の利用の可能性  Industrial applicability
[0056] 本発明の半導体光電極によれば、光の吸収効率を高め、さらに電荷の再結合を防 止することができる。本発明の半導体光電極の製造方法によれば、表面に凹凸が作 成されて表面積を高めた半導体光電極を容易に製造することができる。また本発明 の光エネルギ変換装置によれば、光の吸収効率が高ぐさらに電荷の再結合を防止 できる半導体光電極を用いたため、光電変換効率を高めることができる。 [0056] According to the semiconductor photoelectrode of the present invention, it is possible to increase the light absorption efficiency and prevent charge recombination. According to the method for producing a semiconductor photoelectrode of the present invention, it is possible to easily produce a semiconductor photoelectrode having an uneven surface formed to increase the surface area. Also, according to the light energy conversion device of the present invention, the photoelectric conversion efficiency can be increased because the semiconductor photoelectrode that has high light absorption efficiency and can prevent charge recombination can be used.

Claims

請求の範囲 The scope of the claims
[I] 表面に凹凸を有する金属基板と、  [I] a metal substrate having irregularities on the surface;
前記金属基板の表面に作成され、光触媒作用を有する材料から成る半導体層と、 を有することを特徴とする半導体光電極。  And a semiconductor layer made of a material having a photocatalytic action and formed on the surface of the metal substrate.
[2] 前記金属基板の表面における算術平均粗さは、 1 μ m〜4 μ mの範囲であることを 特徴とする請求項 1に記載の半導体光電極。  [2] The semiconductor photoelectrode according to [1], wherein the arithmetic average roughness on the surface of the metal substrate is in the range of 1 μm to 4 μm.
[3] 前記光触媒作用を有する材料は、 Ti、 Nb、 Ta、 W、 V、 Co、 Fe、 Ni及び Inの中力 選 択される少なくとも 1種以上の元素を含むことを特徴とする請求項 1に記載の半導体 光電極。 [3] The photocatalytic material includes at least one element selected from among Ti, Nb, Ta, W, V, Co, Fe, Ni and In. The semiconductor photoelectrode according to 1.
[4] 前記半導体層の厚さは、 0. 1 m〜l μ mの範囲であることを特徴とする請求項 1に 記載の半導体光電極。  [4] The semiconductor photoelectrode according to [1], wherein the thickness of the semiconductor layer is in the range of 0.1 m to l μm.
[5] 前記光触媒作用を有する材料は、前記金属基板を形成する金属の化合物と異なる ことを特徴とする請求項 1に記載の半導体光電極。  5. The semiconductor photoelectrode according to claim 1, wherein the material having a photocatalytic action is different from a metal compound forming the metal substrate.
[6] 前記金属基板は、金属粒子を接合することにより成る多孔質体であることを特徴と する請求項 1に記載の半導体光電極。 6. The semiconductor photoelectrode according to claim 1, wherein the metal substrate is a porous body formed by bonding metal particles.
[7] 前記金属粒子の粒径は、 1 μ m〜400 μ mの範囲であることを特徴とする請求項 6 に記載の半導体光電極。 7. The semiconductor photoelectrode according to claim 6, wherein the particle size of the metal particles is in the range of 1 μm to 400 μm.
[8] 前記金属粒子の粒径は、 3 μ m〜200 μ mの範囲であることを特徴とする請求項 7 に記載の半導体光電極。 8. The semiconductor photoelectrode according to claim 7, wherein the particle size of the metal particles is in the range of 3 μm to 200 μm.
[9] 表面に凹凸を有する金属基板を作成する工程と、 [9] creating a metal substrate having irregularities on the surface;
前記金属基板の表面に光触媒作用を有する材料から成る半導体層を作成するェ 程と、  Forming a semiconductor layer made of a material having a photocatalytic action on the surface of the metal substrate;
を有することを特徴とする半導体光電極の製造方法。  A method for producing a semiconductor photoelectrode, comprising:
[10] 前記金属基板の表面における算術平均粗さは、 1 μ m〜4 μ mの範囲であることを 特徴とする請求項 9に記載の半導体光電極の製造方法。 10. The method for producing a semiconductor photoelectrode according to claim 9, wherein the arithmetic mean roughness on the surface of the metal substrate is in the range of 1 μm to 4 μm.
[II] 前記金属基板は、複数の金属粒子を圧力または熱により接合することにより作成さ れることを特徴とする請求項 9に記載の半導体光電極の製造方法。  [II] The method for producing a semiconductor photoelectrode according to [9], wherein the metal substrate is formed by joining a plurality of metal particles by pressure or heat.
[12] 前記金属粒子の粒径は、 1 μ m〜400 μ mの範囲であることを特徴とする請求項 1 1に記載の半導体光電極の製造方法。 12. The particle size of the metal particles is in the range of 1 μm to 400 μm. 2. A method for producing a semiconductor photoelectrode according to 1.
[13] 前記金属粒子の粒径は、 3 μ m〜200 μ mの範囲であることを特徴とする請求項 1[13] The particle size of the metal particles is in the range of 3 μm to 200 μm.
2に記載の半導体光電極の製造方法。 2. A method for producing a semiconductor photoelectrode according to 2.
[14] 前記金属基板の表面における凹凸は、粗研磨若しくは化学エッジング法により作 成されることを特徴とする請求項 9に記載の半導体光電極の製造方法。 14. The method for producing a semiconductor photoelectrode according to claim 9, wherein the unevenness on the surface of the metal substrate is created by rough polishing or chemical edging.
[15] 前記半導体層は、前記金属基板と気体とを化学反応させることにより作成されること を特徴とする請求項 9に記載の半導体光電極の製造方法。 15. The method for producing a semiconductor photoelectrode according to claim 9, wherein the semiconductor layer is formed by chemically reacting the metal substrate and a gas.
[16] 前記化学反応は、酸化、窒化及び硫ィ匕の 、ずれかであることを特徴とする請求項 116. The chemical reaction is any one of oxidation, nitridation, and sulfur.
5に記載の半導体光電極の製造方法。 6. A method for producing a semiconductor photoelectrode according to 5.
[17] 前記半導体層は、前記金属基板の表面に光触媒作用を有する材料を含むスラリー を塗布した後、熱処理することにより作成されることを特徴とする請求項 9に記載の半 導体光電極の製造方法。 [17] The semiconductor photoelectrode according to [9], wherein the semiconductor layer is formed by applying a slurry containing a material having a photocatalytic action on the surface of the metal substrate and then performing a heat treatment. Production method.
[18] 請求項 1に記載の半導体光電極を用いた光エネルギ変換装置。 18. A light energy conversion device using the semiconductor photoelectrode according to claim 1.
[19] 請求項 1に記載の半導体光電極を用いた水素製造装置。 19. A hydrogen production apparatus using the semiconductor photoelectrode according to claim 1.
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